To improve the identification of chronic thromboembolic pulmonary hypertension. We restrospectively analysed clinical data of 72 patients with chronic thromboembolic pulmonary hypertension (CTEPH). The levels of arterial blood gases appeared to be decrease in PaO2 and PaCO2, and increase in P(A-a)O2. There were 80.3% of unsymmetrical pulmonary hyperlucencies on chest radiograph and 76.4% of right ventricular hypertrophy on electrocardiograph, 92.5% and 97.1% of right atrial and right ventricular enlargement, respectively. 11.1% of pericardial effusion was noted on echocardiograph, and 98.5% of rise in pulmonary arterial pressure calculated by Doppler. The mean pulmonary arterial pressure was 6.50 +/- 1.80 kPa (48.75 +/- 13.50 mmHg), in part, by right cardiac catheterazation. Both the incidences of pulmonary embolism were 100.0% on pulmonary angiography and on radionuclide lung perfusion scan. There were 43.1% of the history of deep venous disorders and 75.0% of the positive findings by radionuclide venography in the lower extremities, respectively. The misdiagnostic and the lost diagnosis rate of prehospitalization accounted for 90.3%. The understanding of clinical manifestations and laboratory findings of CTEPH is important to promote diagnostic sense and level of CTEPH.